Since the efficiency of a spark ignited internal combustion engine is affected by the amount of spark generated by the ignition system, much effort has been directed to improve on the almost universal use of the Kettering high voltage system.
Neuman U.S. Pat. No. 3,919,993, discloses a dual action ignition system in which the first inductive discharge Kettering circuit initiates spark plug arcing and a second inductive discharge high current low voltage circuit increases the arcing. The two circuits are separated by two "steering diodes" which are necessarily high voltage rectifiers.
These high voltage rectifiers are "strings" of individually selected and matched diodes which are then assembled. They are necessarily expensive with questionable durability since the characteristics of individual diodes will change with temperature and aging.